Ch 7 Section 2 Flashcards
the charges on the ions composing an ionic compound reflect
the electron distribution of the compound
in order to indicate the distribution of electrons among the bonded atoms in a molecular compound/polyatomic ion,
oxidation numbers (oxidation states), are assigned to the atoms composing the compound/ ion
unlike ionic charges, oxidation numbers do not have an
exact physical meaning.
oxidation numbers are useful in
naming compounds, writing formulas, and balancing chemical equations.
as a general rule in assigning oxidation numbers, shared electrons are assumed to belong to
the more electronegative atom in each bond
(Rules for determining oxidation numbers) the atoms in a pure element have an oxidation number of
zero
(Rules for determining oxidation numbers) the more-electronegative element in a binary molecular compound is assigned the number equal to the
negative charge it would have as an anion
(Rules for determining oxidation numbers) the less-electronegative atom is assigned the number equal to the
positive charge it would have as a cation
(Rules for determining oxidation numbers) fluorine has an oxidation number of
-1 in all of its compounds because it’s the most electronegative element.
(Rules for determining oxidation numbers) oxygen has an oxidation number of -2 in almost all compounds. Eceptions include when it is in
peroxides in which its ox # is -1, and when it’s in compounds with fluorine, in which its ox# is +2
hydrogen has an ox number of +1 in all compounds containing elements that are
more electronegative than it; it has an ox # of -1 in compounds with metals
(Rules for determining oxidation numbers) the algebraic sum of the oxidation numbers of all atoms in a neutral compound is
equal to zero
(Rules for determining oxidation numbers) the algebraic sum of the oxidation numbers of all atoms in a polyatomic ion is equal to the
charge of the ion
(Rules for determining oxidation numbers) rules apply to covalently bonded atoms but oxidation numbers can also be assigned to
atoms in ionic compounds
(Rules for determining oxidation numbers) a monatomic ion has an oxidation number equal to the
charge of the ion
because the sum of the oxidation numbers of atoms in a compound must be either zero / equal to charge of ion, it is often possible to
assign oxidation numbers when they are not known
many nonmetals can have more than
one oxidation number
these numbers can sometimes be used in the same manner as ionic
charges to determine formulas.
a formula must represent
facts
oxidation numbers alone cannot be used to prove the
existence of a compound
the stock system is actually based on
oxidation numbers
the stock system can be used as an alternative to the
prefix system for naming binary molecular compounds
the stock system is more practical for
complicated compounds
prefix-based names and stock-system names are still used interchangeably for
many simple compounds
